This invention relates to solar energy collectors, and more particularly to arranging spaced-apart and superimposed cover plates upon the radiation absorbing surface and/or the opposite surface containing an electrical contact for a solar cell. Moreover, the present invention relates to a novel method for bonding such a solar cell onto a support surface through the use of glass pads and electrostatic bonding without the use of adhesives.
Solar cells are conventionally arranged in an array for converting incident solar radiation to electrical power. Each solar cell includes a substrate of semiconductive material of one type conductivity forming a P-N junction with a layer of semiconductive material of the opposite type conductivity. Solar cells of this type, particularly when used in space missions, are vulnerable to thermal damage when exposed to either highly concentrated sunlight or to continuous wave laser energy. The vulnerable components of current solar cell designs are (1) the soldered interconnects between the solar cells and the power distribution network, (2) the adhesive bond between the substrate and the support surface as well as the bond between the cover slide and the cell, (3) the electrical parameters of the solar cell and (4) the cover slide material.
A single cover slide is conventionally adhered to the radiation receiving surface of a solar cell through the use of special-purpose adhesives. Such adhesives frequently have a poor heat conduction property and must remain functional over an extended period of time without deterioration to the solar radiation transmission property. Should the adhesive become opaque to the spectrum of solar radiation particularly useful for conversion to electrical power, then the effectiveness of the solar cell is diminished. The wavelength of solar radiation which is particularly useful for conversion to electrical power through the use of solar cells has an upper cutoff point at about the wavelength of infrared, i.e., not above 5 microns. Thus, it becomes desirable to shield the solar cell from infrared heat energy which has a relatively long wavelength to avoid overheating of the cell and protect the vulnerable components as enumerated hereinbefore.